JP5415111B2 - Method for reducing residual hydrogen concentration of steel bar and pallet for steel bar storage - Google Patents

Description

  The present invention relates to a method for reducing the residual hydrogen concentration of steel bars used for reinforcing bars and the like, and a steel bar storage pallet used therefor.

In general, a steel bar used as a reinforcing bar is manufactured by cutting a hot steel material hot-rolled into a bar shape into an appropriate length with a cold shear or the like. For this reason, when the outer diameter of the steel bar is increased, cracks are likely to occur during cutting of the reinforcing bar or during bending. This is because the residual hydrogen in the steel becomes harder to escape as the outer diameter of the steel bar becomes larger. In order to suppress the occurrence of cracking due to residual hydrogen, the residual hydrogen concentration of the steel bar needs to be 0.5 ppm or less, for example. There is.
However, in a steel bar such as SD390, it is necessary to leave the steel bar for 30 days or more in order to reduce the residual hydrogen concentration to 0.5 ppm or less. For this reason, rust is generated while the steel bar is left unattended, causing a problem that the quality of the steel bar is degraded.

Various methods have been conventionally proposed as a method for lowering the hydrogen concentration in steel materials. For example, Patent Document 1 discloses that a high-temperature steel material after hot working is accommodated in a pit type or cover type slow cooling furnace, and 700 A method is disclosed in which steel material is forcibly cooled after removing about 60% of the hydrogen contained in the steel material by gradually cooling from a high temperature region of from 500C to 500C.
Patent Document 2 discloses that when a steel material is manufactured by heating, rolling, and cooling a slab obtained from molten steel, the hydrogen concentration in the molten steel, the dehydrogenation rate of the slab immediately before heating, the slab at the end of heating. The hydrogen concentration Ho of the final product is calculated based on the dehydrogenation rate of the product, and the dehydrogenation rate when the final product is obtained through rolling, and the final product hydrogen concentration Ho and the crack limit hydrogen concentration D set in advance are obtained. A method is disclosed in which when Ho is greater than D, slabs and / or products after rolling are gradually cooled, and when Ho is less than or equal to D, slow cooling is not performed.

  However, in the method disclosed in Patent Document 1, the steel material after rolling is gradually cooled from a high temperature region of 700 ° C. to 500 ° C. to 500 ° C. to diffuse the hydrogen contained in the steel material. Therefore, it is necessary to provide a pit or a dedicated furnace that can withstand a high temperature of 700 ° C. to 500 ° C. between any of the processes of hot shearing → forced cooling by water cooling → air cooling by a cooling bed. For this reason, not only the steel handling immediately after rolling and hot shearing is once charged in the pit or dedicated furnace and gradually cooled, but the rolling capacity of the rolling mill is limited by the processing capacity of the pit or dedicated furnace. There is a problem of receiving.

On the other hand, in the method disclosed in Patent Document 2, when the thickness of the slab is 1, the hydrogen diffusion distance in the slab stage is halved, which is about 10 times the hydrogen diffusion distance in the product. End up. In addition, if dehydrogenation is performed in the slab stage, the slab is eventually cooled, so that there is a problem that hot charging to the heating furnace cannot be performed.
On the wire material side, as represented by Patent Documents 3 and 4, a method has been proposed in which a wire coil is housed in a dehydrogenation device, hot air is supplied to heat the wire material, and dehydrogenation is performed. However, in the case of a wire rod, the wire diameter is narrower than that of a steel bar, and since the wire coil is wound loosely and bound, there is a large gap between the wires, so there is an advantage that it is easy to heat. However, when trying to apply this technique, it is difficult to heat with steel bars. First of all, it takes a long time to heat the steel bar, and because of the dehydrogenation, even when the wire coil was heated, the heating temperature unevenness was greatly generated. Or, it is necessary to heat for several weeks.

  By the way, as a result of earnest research on reducing the residual hydrogen concentration of the steel bar, the present inventor is used when storing a steel bar obtained by cutting a high-temperature steel material (for example, 200 ° C. or higher) hot rolled into a bar shape. As a steel bar storage pallet to be used, a steel bar storage pallet having heat insulation and outside air blocking properties is used, and by maintaining the bar steel temperature at a predetermined temperature or higher in the steel bar storage pallet, the residual hydrogen concentration of the steel bar becomes 0. The knowledge that it falls to 5 ppm or less was acquired.

Japanese Patent Publication No.57-50851 JP 2005-23413 A Japanese Patent Publication No. 5-57334 Japanese Patent Publication No. 8-935

However, if it is attempted to reduce the residual hydrogen concentration of the steel bar using the above method, the temperature of the steel bar until the steel bar obtained by cutting the hot steel material hot rolled into a bar shape is accommodated in the steel bar storage pallet. Since (surface temperature) is lowered to a temperature lower than a predetermined temperature due to a heat dissipation phenomenon, there is a problem to be solved that the residual hydrogen concentration of the steel bar cannot be reduced to a desired concentration.
The present invention has been made paying attention to the above-mentioned problems, and its purpose is to accommodate a steel bar obtained by cutting a hot steel material hot-rolled into a bar shape in a steel bar storage pallet. The present invention provides a method for reducing the residual hydrogen concentration of a steel bar that can reduce the residual hydrogen concentration of the steel bar to a desired concentration, and a steel bar storage pallet used therefor.

In order to solve the above problems, the method for reducing the residual hydrogen concentration of a steel bar according to the invention of claim 1 is used when storing a steel bar obtained by cutting a hot steel material hot-rolled into a bar shape. As the steel bar storage pallet, a steel bar storage pallet having heat insulation and outside air blocking properties is used, and hot air is supplied into the steel bar storage pallet so that the temperature of the bar steel is kept at a predetermined temperature or higher in the steel bar storage pallet. When reducing the residual hydrogen concentration of the steel bar, the steel bar is bound so that the binding diameter is 250 mm or more and stored in the steel bar storage pallet, and the residual hydrogen concentration of the steel bar is reduced to 0.5 ppm or less. It is characterized by .

The method for reducing the residual hydrogen concentration of a steel bar according to the invention of claim 2 is the method for reducing the residual hydrogen concentration of the steel bar according to claim 1 , wherein the steel bar has a steel bar inside the steel bar storage pallet when the outer diameter of the steel bar is 25 to 29 mm. The temperature is maintained at a temperature of 100 ° C. or higher for 8 hours or longer.
The method for reducing the residual hydrogen concentration of a steel bar according to the invention of claim 3 is the method for reducing the residual hydrogen concentration of the steel bar according to claim 1 , wherein the steel bar is stored in the steel bar pallet when the outer diameter of the steel bar is 30 to 38 mm. Is maintained at a temperature of 150 ° C. or higher for 8 hours or longer.

The method for reducing the residual hydrogen concentration of a steel bar according to the invention of claim 4 is the method for reducing the residual hydrogen concentration of a steel bar according to claim 1 , wherein the steel bar is stored in the steel bar pallet when the outer diameter of the steel bar is 39 to 51 mm. Is maintained at a temperature of 200 ° C. or more for 8 hours or more.
The method for reducing the residual hydrogen concentration of the steel bar according to the invention of claim 5 is the method for reducing the residual hydrogen concentration of the steel bar according to claim 1 or 2 , wherein the cutting temperature of the steel material is when the outer diameter of the steel bar is 25 to 29 mm. It is 100 degreeC or more and 350 degrees C or less, It is characterized by the above-mentioned.
The method for reducing the residual hydrogen concentration of a steel bar according to the invention of claim 6 is the method for reducing the residual hydrogen concentration of the steel bar according to claim 1 or 3 , wherein the cutting temperature of the steel material is when the outer diameter of the steel bar is 30 to 38 mm. It is 150 degreeC or more and 350 degrees C or less, It is characterized by the above-mentioned.

The method for reducing the residual hydrogen concentration of the steel bar according to the invention of claim 7 is the method for reducing the residual hydrogen concentration of the steel bar according to claim 1 or 4 , wherein the cutting temperature of the steel material is when the outer diameter of the steel bar is 39 to 51 mm. It is 200 degreeC or more and 350 degrees C or less, It is characterized by the above-mentioned.
A steel bar storage pallet according to the invention of claim 8 is a steel bar storage pallet used in the method for reducing residual hydrogen concentration of steel bars according to any one of claims 1 to 7 , wherein the heat insulation is formed in a box shape. comprising: a pallet body structure, and a plurality of steel bar cradle in parallel to each other only provided on the bottom surface portion of the pallet body, and a shutter mechanism which shields the upper opening of said pallet body openably said steel bar A hot air generator for supplying hot air to the hot air duct from the outside of the pallet body, and a plurality of hot air ducts for blowing hot air from a plurality of air holes drilled in the upper surface portion of the cradle. It is provided on the pallet body .

According to invention of Claims 1-4 , compared with the case where the hot steel bar obtained by cut | disconnecting the steel material hot-rolled by the bar shape is accommodated in the steel bar storage pallet one by one, the temperature of the steel bar is radiated. The phenomenon makes it difficult to drop to a temperature lower than a predetermined temperature. Therefore, it is possible to reduce the residual hydrogen concentration of the steel bar to 0.5 ppm or less by accommodating the steel bar obtained by cutting the steel material hot-rolled into a bar shape in the steel bar storage pallet.
According to invention of Claims 5-7 , it can suppress that a defect arises in the cut surface of the steel bar obtained by cut | disconnecting the hot steel material hot-rolled by the rod shape.

According to the invention which concerns on Claim 8 , a steel bar can be stored in the state which kept the hot steel bar obtained by cut | disconnecting the steel material hot-rolled by the rod shape at the predetermined temperature.
Further, according to the invention according to claim 8, formed in the upper surface of the receiving bars stand in steel bar placed on the upper surface portion of which the steel bar cradle supplying hot air to the hot air duct from the hot air generator provided in the pallet body Since the air is blown from the air blowing holes, the steel bar can be stored in a state where the temperature of the steel bar is maintained at a predetermined temperature or more even in the winter season when it is easily affected by the outside air.

It is a flowchart for demonstrating the residual hydrogen concentration reduction method of the steel bar which concerns on this invention. Tens of steel bars with an outer diameter of 25 mm obtained by cutting high-temperature steel that has been hot-rolled into a bar shape are bound into dozens of bars and stored in a bar steel storage pallet. It is a figure which shows the result of having measured the steel bar residual hydrogen density | concentration when maintaining at the temperature of 100 degreeC, 150 degreeC, 200 degreeC, and 250 degreeC over 24 hours. Several dozen steel rods with an outer diameter of 29 mm obtained by cutting high-temperature steel that has been hot-rolled into a rod shape are bundled and accommodated in a steel bar storage pallet. It is a figure which shows the result of having measured the steel bar residual hydrogen density | concentration when maintaining at the temperature of 100 degreeC, 150 degreeC, 200 degreeC, and 250 degreeC over 24 hours. Tens of bar steels with an outer diameter of 38 mm obtained by cutting high-temperature steel material hot-rolled into a bar shape are bound into dozens of bars and stored in a bar steel storage pallet. It is a figure which shows the result of having measured the steel bar residual hydrogen density | concentration when maintaining at the temperature of 100 degreeC, 150 degreeC, 200 degreeC, 250 degreeC, 275 degreeC, and 300 degreeC over 24 hours. Several dozen steel bars with an outer diameter of 51 mm obtained by cutting high-temperature steel that has been hot-rolled into a rod shape are bundled and accommodated in a steel bar storage pallet. It is a figure which shows the result of having measured the steel bar residual hydrogen density | concentration when maintaining at the temperature of 100 degreeC, 150 degreeC, 200 degreeC, 250 degreeC, 275 degreeC, and 300 degreeC over 24 hours. It is a figure which shows typically the flow of a hot air in the case of heating the steel bar bound by dozens of wires with a binding wire with a hot air. It is a top view which shows an example of the pallet for steel bar storage used when storing the steel bar obtained by cut | disconnecting the hot steel material hot-rolled by the rod shape. It is a side view of the pallet for steel bar storage shown in FIG. It is a figure which shows the AA cross section of FIG. It is a figure which shows the BB cross section of FIG.

  A method for reducing the residual hydrogen concentration of a steel bar according to an embodiment of the present invention is shown in FIG. As shown in the figure, the method for reducing the residual hydrogen concentration of a steel bar according to an embodiment of the present invention first cuts a hot steel material hot-rolled into a bar shape into an appropriate length using a cold shear or the like. The obtained straight bar-shaped steel bars are bound to several tens by an automatic binding machine, and then housed in a steel bar storage pallet having heat insulation and outside air blocking properties using a lifting machine such as a lifting magnet (steps S1, S2). ). The reason why the number of bundles is set to ten to several tens is to prevent the temperature drop until the next step of storage in the steel bar storage pallet by setting the steel bar binding diameter to 250 mm or more. When the binding diameter of the steel bar is at least 250 mm or more, even if the surface temperature of the steel bar on the outer periphery is lowered, it becomes easy to reheat in the steel bar storage pallet having heat insulation and outside air blocking properties. Then, the temperature of the steel bar in the steel bar storage pallet is 8 hours or more, preferably 16 hours or more, over a predetermined temperature (for example, 100 ° C. or more when the steel bar has an outer diameter of 25 to 29 mm, and 30 to 38 mm. The residual hydrogen concentration of the steel bar is set to 0.5 ppm or less, for example, by maintaining the temperature at 150 ° C. or more and 200 ° C. or more in the case of 39 to 51 mm (step S3).

  In addition, when cutting hot steel material hot-rolled into a rod shape with a cold shear or the like, if the cutting temperature of the steel material exceeds 350 ° C., it becomes close to the brittle temperature of the steel material, and the cut surface of the steel bar obtained by cutting the steel material When the outer diameter of the steel bar is 25 to 29 mm, the cutting temperature of the steel is 100 ° C. or higher and 350 ° C. or lower, and when the outer diameter of the steel bar is 30 to 38 mm, the steel material has a brittle defect. When the cutting temperature is 150 ° C. or more and 350 ° C. or less and the outer diameter of the steel bar is 39 to 51 mm, the cutting temperature of the steel material is preferably 200 ° C. or more and 350 ° C. or less.

  As described above, as a steel bar storage pallet used when storing steel bars obtained by cutting hot steel that has been hot-rolled into a bar shape, a steel bar storage pallet having heat insulation and outside air blocking properties is used. In order to reduce the residual hydrogen concentration of the steel bar by keeping the steel bar temperature above a predetermined temperature for 8 hours or more in this steel bar storage pallet, when the steel bar is bound into several tens of bars and stored in the steel bar storage pallet Compared with the case where the steel bars are stored one by one in the steel bar storage pallet, the temperature of the steel bars is less likely to fall below a predetermined temperature due to the heat dissipation phenomenon. Therefore, the steel bar obtained by cutting the hot steel material hot-rolled into a bar shape can be accommodated in the steel bar storage pallet, and the residual hydrogen concentration of the steel bar can be reduced to a desired concentration.

In addition, after hot-rolled hot-rolled steel material is cut to a suitable length and then gradually cooled, rolling → hot shear → cooling by water cooling → air cooling by cooling floor → by cold shear to product length It can be carried out without disturbing a series of processes such as cutting, and does not hinder rolling. Furthermore, since it can process by raising the temperature at the time of a cutting | disconnection, a rolling capability can also be raised.
In addition, in order to keep the steel bar obtained by cutting the hot steel material hot-rolled into a bar shape at a predetermined temperature, a conventional pit or dedicated furnace that can withstand high temperatures for slow cooling in a high temperature range. The residual hydrogen concentration of the steel bar can be reduced to a desired concentration within the steel bar storage pallet without holding the steel, which is economical and does not cause rolling restrictions.

Furthermore, the dehydrogenation treatment can be performed in a short time, the bar steel can be shipped quickly, and a bar steel that is difficult for processing cracks to be generated by the customer can be provided.
Tens of steel bars with an outer diameter of 25 mm obtained by cutting high-temperature steel that has been hot-rolled into a bar shape are bound into dozens of bars and stored in a bar steel storage pallet. FIG. 2 shows the results of measuring the residual hydrogen concentration of the steel bar when kept at temperatures of 100 ° C., 150 ° C., 200 ° C., and 250 ° C. for 24 hours.

In addition, dozens of steel rods with an outer diameter of 29 mm obtained by cutting high-temperature steel that has been hot-rolled into a rod shape are bundled and accommodated in a steel bar storage pallet, and the temperature of the steel bar is controlled in the steel bar storage pallet. FIG. 3 shows the results of measuring the residual hydrogen concentration of the steel bar when kept at temperatures of 100 ° C., 150 ° C., 200 ° C., and 250 ° C. for 8 to 24 hours.
As shown in FIG. 2, several tens of steel bars having an outer diameter of 25 mm are bound and the temperature of the steel bars is kept in the steel bar storage pallet for 8 hours or more, preferably 16 hours or more, preferably 100 ° C. or more, preferably 150 ° C. It can be seen that when the above temperature is maintained, the residual hydrogen concentration of the steel bar decreases to 0.5 ppm or less.

In addition, as shown in FIG. 3, several tens of steel bars having an outer diameter of 29 mm are bundled and the temperature of the steel bars is kept in the steel bar storage pallet for 8 hours or more, preferably 16 hours or more, preferably 100 ° C. or more, preferably It can be seen that when the temperature is maintained at 150 ° C. or higher, the residual hydrogen concentration of the steel bar decreases to 0.5 ppm or less.
Accordingly, when the outer diameter of the steel bar is 25 to 29 mm, the steel bar hot-rolled into a bar shape is obtained by maintaining the steel bar temperature at 100 ° C. or higher for 8 hours or longer in the steel bar storage pallet. The obtained hot steel bar can be housed in a steel bar storage pallet to reduce the residual hydrogen concentration of the steel bar to 0.5 ppm or less.

Tens of bar steels with an outer diameter of 38 mm obtained by cutting high-temperature steel material hot-rolled into a bar shape are bound into dozens of bars and stored in a bar steel storage pallet. FIG. 4 shows the results of measuring the residual hydrogen concentration of the steel bar when kept at temperatures of 100 ° C., 150 ° C., 200 ° C., 250 ° C., 275 ° C., and 300 ° C. for 24 hours.
As shown in FIG. 4, several tens of steel bars having an outer diameter of 38 mm are bundled and the temperature of the steel bars is set to 150 ° C. or more, preferably 200 ° C. for 8 hours or more, preferably 16 hours or more in the steel bar storage pallet. It can be seen that when the above temperature is maintained, the residual hydrogen concentration of the steel bar decreases to 0.5 ppm or less.

Accordingly, when the outer diameter of the steel bar is 30 to 38 mm, the steel bar hot-rolled into a bar shape is obtained by maintaining the steel bar temperature at 150 ° C. or higher for 8 hours or longer in the steel bar storage pallet. The obtained hot steel bar can be housed in a steel bar storage pallet to reduce the residual hydrogen concentration of the steel bar to 0.5 ppm or less.
Several dozen steel bars with an outer diameter of 51 mm obtained by cutting high-temperature steel that has been hot-rolled into a rod shape are bundled and accommodated in a steel bar storage pallet. FIG. 5 shows the results of measuring the residual hydrogen concentration of the steel bar when kept at temperatures of 100 ° C., 150 ° C., 200 ° C., 250 ° C., 275 ° C., and 300 ° C. for 24 hours.

As shown in FIG. 5, several tens of steel bars having an outer diameter of 51 mm are bundled, and the temperature of the steel bar is set to 200 ° C. or more, preferably 250 ° C. for 8 hours or more, preferably 16 hours or more in the steel bar storage pallet. It can be seen that when the above temperature is maintained, the residual hydrogen concentration of the steel bar decreases to 0.5 ppm or less.
Accordingly, when the outer diameter of the steel bar is 39 to 51 mm, the steel bar hot-rolled into a bar shape is obtained by maintaining the steel bar temperature at 200 ° C. or higher for 8 hours or longer in the steel bar storage pallet. The obtained hot steel bar can be housed in a steel bar storage pallet to reduce the residual hydrogen concentration of the steel bar to 0.5 ppm or less.

[Comparative Example 1]
The steel bar obtained by cutting the billet hot-rolled into a bar shape was bound to about 20 to 40 steel bars with a binding wire, and then the steel bar at normal temperature was heated with hot air to dehydrogenate the steel bar. The flow of hot air at this time is shown in FIG. As shown in the figure, the hot air 12 for heating the steel bar 11 mainly flows outside the binding wire 13 that binds the steel bar 11, so the steel bar 11 on the surface near the binding wire 13 is hot air 12. However, the portion away from the binding wire 13, that is, the steel bar 11 located inside, was hardly heated by the hot air 12. In the case of a steel bar, it is assumed that the hot air 12 is difficult to enter inside because it is a straight bar and is bound so as to be in contact with each other, and the surface remains heated.

[Comparative Example 2]
When manufacturing reinforced concrete steel bar SD390, billet was used as a rolling material, subjected to dehydrogenation treatment by slow cooling in a high temperature region for 72 hours, and then reheated and subjected to rolling. The lead time required 88 hours including slow cooling time, conveyance time, and rolling time.
[Example 1]
When manufacturing the steel rod SD390 for reinforced concrete similarly to the comparative example 2, billet was used as a raw material of a steel bar. And after binding the 50 steel bars obtained by cutting the billet hot-rolled into a bar shape with a cold shear at a temperature of 250 ° C., it is 8 hours in a steel bar pallet for heat insulation and outside air shielding. The dehydrogenation treatment was performed while maintaining the temperature at 200 ° C. or higher. Subsequent cooling required 16 hours, but it was possible to manufacture in 28 hours including heat rolling. The steel bar was transported to the steel bar storage pallet using a lifting magnet, and there was no hindrance to handling above 200 ° C.

[Example 2]
A windbreak was attached to the winter cooling floor to prevent the temperature drop of the steel bar, and the cutting temperature in the cold shear was adjusted to 250 ° C. and cut. For easy handling, as shown in Table 1, the steel bar diameter is 51 mm: 15 bar units, the steel bar diameter is 41 mm: 20 bar units, the bar steel diameter is 38 mm: 30 bar units, the bar steel diameter is 35 mm: 40 bar units, and the bar steel diameter is as shown in Table 1. The unit was 32 mm: 50 units, the steel bar diameter was 29 mm: 60 units, and the binding diameter was 250 mm or more. The heat retention in the steel bar storage pallet was 200 ° C. or more, and dehydrogenation of 0.5 ppm or less could be achieved by holding for 8 hours.

[Example 3]
Cutting was performed by increasing the conveying speed of the cooling bed and adjusting the cutting temperature in the cold shear to 290 ° C. The heat retention in the steel bar storage pallet was 200 ° C. or more, and dehydrogenation of 0.5 ppm or less could be achieved by holding for 8 hours.
Next, an example of a steel bar storage pallet used in the steel bar residual hydrogen concentration reducing method according to the present invention is shown in FIGS. The steel bar storage pallet 20 shown in FIGS. 7 to 10 includes a pallet body 21 having a heat insulating structure formed in a box shape, and a plurality of bar cradles 22 arranged in parallel to each other on the bottom surface of the pallet body 21. It has.

Further, the steel bar storage pallet 20 is provided with a shutter mechanism 23 that shields the upper opening of the pallet main body 21 so that it can be opened and closed. The pallet main body 21 has a plurality of air holes drilled in the upper surface of the bar steel base 22. Hot air ducts 25 and 26 for blowing hot air for keeping warm from 24 are provided, and a hot air generator 27 for supplying hot air to the hot air ducts 25 and 26 from the outside of the pallet main body 21 is provided.
When the above-described steel bar storage pallet 20 is used as a steel bar storage pallet as a steel bar storage pallet used when storing hot steel bars obtained by cutting a steel material that has been hot rolled into a bar shape, it is hot rolled into a bar shape. The high-temperature steel bar obtained by cutting the formed steel material can be stored in a state kept at a predetermined temperature or higher.

  Further, since hot air is supplied from the hot air generator 27 provided in the pallet main body 21 through the hot air ducts 25 and 26 into the pallet main body 21 to keep the heat, the steel bar is affected by the outside air and is easily cooled even in the winter season. The steel bar can be stored in a state in which the temperature is maintained at a predetermined temperature or higher. The hot air is directly blown out and supplied from the hot air ducts 25 and 26 into the pallet, and the hot air supplied to the hot air ducts 25 and 26 is supplied to the steel bar pedestal 22 through a ventilation path formed in the bar steel pedestal 22. You may make it supply so that it may blow off from the ventilation hole 24 provided in the upper surface part.

DESCRIPTION OF SYMBOLS 11 Steel bar 12 Hot air 13 Bundling wire 20 Steel bar storage pallet 21 Pallet main body 22 Steel bar cradle 23 Shutter mechanism 24 Blower hole 25, 26 Hot air duct 27 Hot air generator

Claims (8)

As a steel bar storage pallet used to store steel bars obtained by cutting hot steel that has been hot-rolled into a bar shape, a steel bar storage pallet with heat insulation and outside air blocking properties is used. In order to reduce the residual hydrogen concentration of the steel bar by supplying hot air into the steel pallet and maintaining the temperature of the steel bar above the predetermined temperature in the steel bar storage pallet , the steel bar is bound so that the binding diameter is 250 mm or more. And reducing the residual hydrogen concentration of the steel bar to 0.5 ppm or less by storing it in the steel bar storage pallet. The residual hydrogen concentration reduction of steel bars according to claim 1, wherein the maintaining the temperature above 100 ° C. The temperature for more than 8 hours of bars in bars archival palette when the outer diameter 25~29mm of the bars Method. Residual hydrogen concentration in the steel bar according to claim 1 having an outer diameter and wherein the maintaining the temperature above with steel bar storage pallets in the temperature of the steel bars for more than 8 hours of 0.99 ° C. or higher when the 30~38mm of the bars Reduction method. Residual hydrogen concentration in the steel bar according to claim 1 having an outer diameter and wherein the keep the steel bar storage pallets in the above 200 ° C. The temperature of the steel bars for more than 8 hours at a temperature at 39~51mm of the bars Reduction method. The method for reducing the residual hydrogen concentration of a steel bar according to claim 1 or 2 , wherein the cutting temperature of the steel material is 100 ° C or higher and 350 ° C or lower when the outer diameter of the steel bar is 25 to 29 mm. The method for reducing the residual hydrogen concentration of a steel bar according to claim 1 or 3 , wherein a cutting temperature of the steel material is 150 ° C or higher and 350 ° C or lower when the outer diameter of the steel bar is 30 to 38 mm. The method for reducing the residual hydrogen concentration of a steel bar according to claim 1 or 4 , wherein when the outer diameter of the steel bar is 39 to 51 mm, the cutting temperature of the steel material is 200 ° C or higher and 350 ° C or lower. A steel bar storage pallet used in the method for reducing residual hydrogen concentration of a steel bar according to any one of claims 1 to 7 , wherein the pallet body has a heat insulating structure formed in a box shape, and a bottom part of the pallet body. a plurality of bars cradle arranged parallel to each other provided only the pallet and a shutter mechanism for opening and closing freely shielding an upper opening of the main body, a plurality of blowing bored in the upper surface portion of the steel bar cradle A plurality of hot air ducts for blowing hot air from holes are provided in the pallet main body, and a hot air generator for supplying hot air to the hot air duct from the outside of the pallet main body is provided in the pallet main body . palette.

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